With regard to the video: I think it goes to much in to practical detail at first. I would like to come at this from a more abstract level.
What is the purpose of being able to always serve a higher purpose?
You are conscious. Consciousness is ALL there is. Consciousness creates purpose. Become more consciousness and you find (create) more purpose in life. There is no end to that. Just likea fractal has no end and can become more and more complex when energy is put in to the formula to create a fractal. Consciousness wants (needs) to evolve. So the purpose of us all is to learn how to create synergy. As that is how we grow. So in the most abstract concept, your life's purpose is exactly the same as mine.
The videos five questions can be derived from the purpose, that ALL there is (which is conscious) wants (needs) to evolve.
Now you can go into more detail. How can I serve ALL there is? By creating synergy. Doing what you are good at. Because you can create more synergy with what your good at than by struggling with things you s*ck at in a certain period of time.
Now derive his 5 questions from the concept above, and I think that is your answer.
To touch a little more upon what the video says:
He talks about finding out what other people need and how to make them happy. Altruism is key to serving a larger system. The opposite, ego, is destructive for a larger system. If you create synergy with someone else, you become more, and that person becomes more. So in that case you are also altruistic, because you serve what they need.
Only looking at your title:
I could have typed: Find a purpose by asking whether you could be of help to someone (in the scheme of creating synergy, not by serving their ego's). Than there is a purpose. :D Just kidding though!